Production of a Platinum-Free Chelate Catalyst Material as an Intermediate Product, and Further Processing Thereof to Obtain an Electrocatalytic Coating as a Final Product

Abstract

A method for preparing a platinum-free chelate catalyst material as an intermediate product for selective electrocatalytic reduction of oxygen includes performing a low-temperature plasma treatment on a powdery form of the transition-metal chelate in a plasma reactor chamber having an inert plasma gas disposed therein. A plasma power, a plasma gas pressure, a plasma initialization and a treatment time of the low-temperature plasma treatment are selected so that molecules of the transition metal chelate are fragmented in the plasma and cross-link in a subsequent chemical reaction so as to form a carbon matrix and retain a basic chelate structure in a surrounding of the transition metal.

Description

CROSS REFERENCE TO PRIOR APPLICATION[0001]This is a U.S. National Phase application under 35 U.S.C. §371 of International Application No. PCT / DE2006 / 000326, filed Feb. 20, 2006 and claims the benefit of German Patent Application No. 10 2005 008 338.2, filed on Feb. 20, 2005. The International Application was published in German on Aug. 24, 2006 as WO 2006 / 086979 under PCT Article 21 (2).FIELD OF THE INVENTION[0002]The present invention relates to a method for preparing a platinum-free chelate catalyst material as an intermediate product for the selective electrocatalytic reduction of oxygen, having a porous, conductive carbon matrix containing embedded, electrochemically active centers of a transition-metal chelate, and to a method for further processing the intermediate product to obtain an electrocatalytic coating as a final product on a substrate, as well as to an application of the final product.BACKGROUND[0003]Platinum-free chelate catalyst material for the electrocatalytic red...

AI Technical Summary

Benefits of technology

[0020]Therefore, it is an object of the present invention to provide a method for preparing a platinum-free chelate catalyst material with improved catalyzing capacity in such a way that the particles are prevented from sintering together during the reaction. It is intended, additionally and alternatively to provide a product made of nm-scale particles having a highly catalytically active surface. It is also alternatively intended that, from this product, a final product in the form of an electrocatalytic coating, particularly suited for gas-diffusion electrodes, be obtainable as an intermediate product in a simple, efficient, and cost-effective manner.

Problems solved by technology

When methanol is used as fuel for fuel cell operation (in the case of a direct-methanol fuel cell), cathode poisoning occurs when platinum is used as a catalyst.

However, the chelate catalyst material known from the related art having chelate molecules adsorbed onto a carbon black support material and treated in a high-temperature process, exhibits unsatisfactory catalytic performance characteristics.

This is due to the disadvantageous surface quality of the material.

Catalytic centers are located inside of the reaction layer and are, therefore, not able to take part in the oxygen reduction.

If the chelate molecule is treated without the use of a carbon black support material in order to obtain a higher center density in the high-temperature reaction, then the disadvantage of this process becomes even more clearly apparent.

However, these films exhibit low electrical conductivity properties that are not selective.

Although these automated preparation processes have paved the way from the factory to industrial production of gas-diffusion electrodes, the methods mentioned are disadvantageously characterized by an ex-situ preparation of the catalyst and a high loss of catalyst material during the process.

Although the active catalyst particles are located exclusively on the electrochemically accessible surface, and a high dispersion is achieved, thereby creating a suitable bounding surface for the electrochemical processes to occur later, the catalyst particles produced in this process are still too large (150 nm) to permit an effective catalysis.

However, there is no discussion of a simultaneous chemical reaction and creation of a new substance having particles in the nanoscale range.

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